Search results for "cyclic"

Electrochemical incineration of 1,2-dichloroethane: Effect of the electrode material

2008

The electrochemical incineration of 1,2-dichloroethane (EDC) at Pt, Au, boron-doped diamond (BDD), Ebonex, stainless steel, Ti/IrO2–Ta2O5 and PbO2 has been studied in acid media by cyclic voltammetry and bulk electrolysis. It has been shown that the performances of the process dramatically depend on the anodic material. Higher current efficiencies were obtained at BDD. In particular, at proper values of applied current density, it is possible to obtain the almost complete conversion of EDC to CO2 at BDD with current efficiencies higher than 40%.

Electrochemical reduction and carboxylation of halobenzophenones

2002

Abstract The electrochemical reduction of a series of halogenated benzophenones XC6H4COC6H4Y (1) was studied in aprotic solvents, in the absence and presence of CO2, by cyclic voltammetry (CV) and controlled-potential electrolysis. The mechanism of electroreduction in dimethylformamide (DMF) has been investigated in some detail. Most of the compounds undergo reductive carbonhalogen bond cleavage in the time window of CV. The radical anions derived from difluorobenzophenones (X=Y=4-F; X=2-F, Y=4-F) as well as from the 3-chloro derivative are quite stable with a cleavage rate constant (kc) of the order of 10−2 s−1 or less. With 4-chloro-, 2-chloro-, 4,4′-dichloro- and 2,4′-dichorobenzophen…

Aromaticity in Pericyclic Transition State Structures? A Critical Rationalisation Based on the Topological Analysis of Electron Density

2016

The nature of the electron delocalisation pattern within a cyclic structure, i. e. the aromatic character, is examined for six-membered pseudocyclic transition state structures (TSs) involved in five representative examples of so-called pericyclic reactions. Results of the electron localisation function (ELF) and the quantum theory of atoms in molecules (QTAIM) analyses of the electron density evidence that in four of the cases, at least one pair of atoms are not bound at the TS configuration, thus precluding a possible cyclic conjugation. These findings make it possible to rule out the aromatic character of these TSs. High values of the synchronicity Sy index at the TSs contrast with the b…

The Mysticism of Pericyclic Reactions: A Contemporary Rationalisation of Organic Reactivity Based on Electron Density Analysis

2018

A molecular electron density theory study for [3 + 2] cycloaddition reactions of 1‐pyrroline ‐1‐oxide with disubstituted acetylenes leading to bicycl…

2020

Nature of the ring-closure process along the rearrangement of octa-1,3,5,7-tetraene to cycloocta-1,3,5-triene from the perspective of the electron lo…

2011

We analyze the behavior of the energy profile of the ring-closure process for the transformation of (3Z,5Z)-octa-1,3,5,7-tetraene 5 to (1Z,3Z,5Z)-cycloocta-1,3,5-triene 6 through a combination of electron localization function (ELF) and catastrophe theory (CT). From this analysis, concepts such as bond breaking/forming processes, formation/annihilation of lone pairs, and other electron pair rearrangements arise naturally through the reaction progress simply in terms of the different ways of pairing up the electrons. A relationship between the topology and the nature of the bond breaking/forming processes along this rearrangement is reported. The different domains of structural stability of …

Unusual B4N2C2 Ligand in a Ruthenium Pseudo-Triple-Decker Sandwich Complex Displaying Three Reversible Electron-Transfer Steps

2007

Chromatographic and spectroscopic properties of regioisomers of some 1H-1,5-benzodiazepines

1994

The separation of the two regioisomeric derivatives of 1H-1,5-benzodia- zepine yielded from the reaction of 1,2-diamino-4-methylbenzene with 4-substituted acetophenones was performed by reversed phase high per- formance liquid chromatography, and the absorption spectra of the sepa- rated isomers have been determined for three isomer pairs which have been obtained starting from acetophenones with substituents of different electronegativity. The isomer ratio then could be estimated as well from the ratio of the peak areas as from the absorption spectra. They agree well with the known ratio determined from nmr intensities

Most of the field/inductive substituent effect works through the bonds

2019

AbstractAn application of the quantum chemical modeling allowed to investigate the nature of the field/inductive substituent effect (SE). For this purpose, series of X-tert-butyl···tert-butane (TTX) complexes (where X = NMe2, NH2, OH, OMe, Me, H, F, Cl, CF3, CN, CHO, COMe, CONH2, COOH, NO2, NO) were studied. A starting distance between central carbon atoms in substituted and unsubstituted fragments of TTX, dC1–C4, was the same as the distance C1–C4 in X-substituted bicyclo[2.2.2]octane (BCO), where the SE acts both via bonds and via space. A strength of interaction between substituted and unsubstituted components of TTX was described by deformation and interaction energies. The substituent …

First Reactions of 2,2′-Bisindolyls with Electrophilic Azo Compounds and Diethyl Mesoxalate

1992

Conformations and some electronic properties of the 2,2′-bisindolyls 6 were calculated for the prediction of probable Diels-Alder reactivity, in analogy to previous work on 2-vinylindoles. First reactions with dienophiles revealed that compounds 6 did not participate in [4 + 2]cycloadditions but rather underwent simple electrophilic substitutions at the enamine function with, above all, some heterodienophiles. Erste Reaktionen von 2,2′-Bisindolylen mit elektrophilen Azoverbindungen und Diethylmesoxalat Zur Vorhersage moglicher Diels-Alder-Reaktionen an 2,2′-Bisindolylen 6 werden Berechnungen zur Konformation und uber elektronische Eigenschaften durchgefuhrt. Die erstmals durchgefuhrten Reak…